The present invention relates generally to modification of the lens member component for an automotive lamp unit having an inner surface with prism elements to focus light transmitted therethrough and further being adapted for direct bonding at an outer rim section to a reflector member of the lamp unit to provide a leak-proof enclosure. Said automotive lamp unit construction has particular utility for automotive headlights. Circular shaped headlights having such lens member construction have been used in motor vehicles for some time and are generally constructed of glass members permitting hermetic sealing of the unit by a reliable fusion seal. Rectangular shaped headlight units have also been introduced along with lamp units using lens and reflector members made of light transparent thermoplastic polymer materials and wherein the lens and reflector members can be bonded directly together with adhesives to provide a leak-proof enclosure.
In most of the automotive lamp units of this type now being used, however, both lens and reflector members have a generally symmetrical contour for ease of molding during manufacture as well as for ease of subsequent assembly together. Automotive lamp units of said conventional design are thereby assembled by bonding together at the rim regions of both reflector and lens members to provide vertical alignment of the smooth exterior surface of the lens member with respect to the longitudinal major axis of the lamp unit. Understandably, such conventional lamp unit construction produces maximum wind resistance when these lamp units are mounted at the front end of the automotive vehicle, such as headlights, fog lights, and the like.
It should further be appreciated that the light beam patterns for vehicle headlamps and vehicle foglights are substantially dissimilar. The light beam from a foglight is projected downwardly to reach the ground a short distance ahead of the vehicle. Any longer projection of this light beam is deemed objectionable since reflection by the fog droplets can produce considerable glare to the vehicle occupants. Accordingly, the prism elements for the foglight lens are specifically constructed to prevent light projection above a horizontal plane as evident in French patent No. 1,401,848, British patent No. 408,113, and Italian patent No. 573,924. Vehicle headlamps are required to project a light beam for a considerable distance from the vehicle, hence the prism elements of a lens member must direct the light forwardly rather than in a downward direction. For the most part, this is accomplished with the lens member aligned in a vertical direction and which can still produce some glare to the occupants of oncoming vehicles. Although tilted mounting of vehicle headlamps is known to provide aerodynamic streamlining, the accepted practice still maintains the lens member of the headlamp itself in a vertically aligned direction as evident in British patent No. 511,687 and recently issued U.S. Pat. No. 4,249,232. In the one known vehicle headlamp having a tilted lens member for aerodynamic streamlining (British patent No. 1,158,069), there is said to be no modification of the prism elements in order to reduce the glare problems thereby created. The known vehicle headlamp and foglight devices are also not of an all glass seal beam type construction but rather employ additional structural components not providing a hermetically sealed lamp enclosure for durability and long life.